import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        double a=0;
        int n = in.nextInt();
        int[] calories = new int[n];
        for(int calories_i=0; calories_i < n; calories_i++){
            calories[calories_i] = in.nextInt();
        }
      a=a+(calories[1] * Math.pow(2,0));
      a=a+(calories[2] * Math.pow(2,1));
         a=a+(calories[0] * Math.pow(2,2));
        int b=(int)a;
        System.out.println(b);
}
}